qualitative analysis

• What are anions also known as?

  Negative ions
• How can you test for carbonate ions, CO$_3^{2-}$?


  Add strong acid and collect gas
• What are the observations for a positive test of carbonate ions, CO$_3^{2-}$?


  Fizzing and limewater turns cloudy
• Write an equation for the carbonate ion test.

  CO$_3^{2-}$ (aq) + 2H$^+$ (aq) → H$_2$O (aq) + CO$_2$ (g)
• How can you test for sulfate ions, SO$_4^{2-}$?


  Add dilute hydrochloric acid and barium chloride
• What are the observations for a positive test of sulfate ions, SO$_4^{2-}$?


  White precipitate of barium sulfate
• Write an equation for the sulfate ion test.

  Ba$^{2+}$ (aq) + SO$_4^{2-}$ (aq) → BaSO$_4$ (s)
• What do you use to test for halide ions?

  Acidified AgNO$_3$
• Why do you add HNO$_3$ to test for halide ions instead of HCl?


  To remove CO$_3^{2-}$ ions
• How can you test for a halide ion?

  Dissolve sample, add AgNO$_3$, record color change
• What is the result and equation for the Cl$^-$ test?


  White precipitate, soluble in dilute ammonia
• Write the equation for the Cl$^-$ test.


  Ag$^+$ (aq) + Cl$^-$ (aq) → AgCl (s)
• What is the result and equation for the Br$^-$ test?


  Cream ppt, soluble in concentrated ammonia only
• Write the equation for the Br$^-$ test.


  Ag$^+$ (aq) + Br$^-$ (aq) → AgBr (s)
• What is the result and equation for the I$^-$ test?


  Yellow precipitate, insoluble in both ammonia
• Write the equation for the I$^-$ test.


  Ag$^+$ (aq) + I$^-$ (aq) → AgI (s)
• When testing for carbonate, sulfate, and halide ions, in which order should the tests be carried out?


  Carbonate, sulfate, halide
• Why should the tests be carried out in that order?

  To avoid insoluble precipitates interfering
• What are cations also known as?

  Positive ions
• How can you test for ammonium ions, NH$_4^{+}$?


  Add sodium hydroxide and warm it
• What are the observations for a positive ammonium ions test?

  Red litmus paper turns blue
• Write the equation for ammonium ions test.

  NH$_4^{+}$ (aq) + OH$^{-}$ (aq) → NH$_3$ (aq) + H$_2$O (aq)
• What are the steps to test for carbonate ions?

  1. Add strong acid to the sample
  2. Collect the gas produced
  3. Pass through lime water
• What are the steps to test for sulfate ions?

  1. Add dilute hydrochloric acid
  2. Add barium chloride to the sample
• What are the steps to test for halide ions?

  1. Dissolve the sample in water
  2. Add aqueous silver nitrate
  3. Record the color change
  4. If needed, add aqueous ammonia
  5. Note the solubility of precipitate
• What is the order of tests for carbonate, sulfate, and halide ions?

  1. Carbonate test
  2. Sulfate test
  3. Halide test
• Why is the order of tests important?

  • To prevent insoluble precipitates from interfering
  • To ensure accurate identification of ions